/*

Given an array of numbers. Print all the pairs (2) of numbers in the array if the sum of those numbers is also present in the array. 

​

Input

int a[] = {10, 5, 2, 7, 7, 49}

Output  (5,2)

*/

​

using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        int[] a = new int[]{12, 10, 5, 2, 7, 7, 49};

        HashSet<int> possibleSums = new HashSet<int>(a);

        for (int i = 0; i < a.Length - 1; i++)

        {

            for (int j = i + 1; j < a.Length; j++)

            {

                int pairSum = a[i] + a[j];

                if (possibleSums.Contains(pairSum)) 

                {

                    Console.WriteLine("({0},{1})", a[i], a[j]);

                }

            }

        }

    }

}